Meconium ileus caused by mutations in GUCY2C, encoding the CFTR-activating guanylate cyclase 2C

Meconium ileus, intestinal obstruction in the newborn, is caused in most cases by CFTR mutations modulated by yet-unidentified modifier genes. We now show that in two unrelated consanguineous Bedouin kindreds, an autosomal-recessive phenotype of meconium ileus that is not associated with cystic fibrosis (CF) is caused by different homozygous mutations in GUCY2C, leading to a dramatic reduction or fully abrogating the enzymatic activity of the encoded guanlyl cyclase 2C. GUCY2C is a transmembrane receptor whose extracellular domain is activated by either the endogenous ligands, guanylin and related peptide uroguanylin, or by an external ligand, Escherichia coli (E. coli) heat-stable enterotoxin STa. GUCY2C is expressed in the human intestine, and the encoded protein activates the CFTR protein through local generation of cGMP. Thus, GUCY2C is a likely candidate modifier of the meconium ileus phenotype in CF. Because GUCY2C heterozygous and homozygous mutant mice are resistant to E. coli STa enterotoxin-induced diarrhea, it is plausible that GUCY2C mutations in the desert-dwelling Bedouin kindred are of selective advantage.     

Endoplasmic Reticulum Stress Induces a Caspase-dependent N-terminal Cleavage of RBX1 Protein in B Cells

Endoplasmic reticulum (ER) stress develops when the ER is overloaded with too many proteins to fold. This elicits a signaling pathway called the unfolded protein response. The unfolded protein response is physiologically required for the terminal development of B cells into antibody-secreting plasma cells. Ring Box Protein 1 (RBX1) is a 14-kDa protein necessary for ubiquitin ligation activity of the multimeric cullin ring ubiquitin ligases (CRLs). As RBX1 is shared by a large number of CRLs, alterations in its activity may lead to global changes in protein stability. We discovered that RBX1 is cleaved in the course of LPS-induced plasma cell differentiation and in multiple myeloma cell lines upon induction of pharmacological ER stress. The cleavage is executed by several caspase proteases that cleave RBX1 eight amino acids from the N terminus. To address the possible implication of RBX1 cleavage for CRL activity, we replaced the endogenous RBX1 homolog of the yeast Saccharomyces cerevisiae, Roc1, with the wild type or the N-terminal Δ8 mutant human RBX1. We show that yeast expressing the cleaved RBX1 are hypersensitive to ER stress and are impaired in CRL-mediated ubiquitination and degradation. We propose a model by which N-terminal cleavage of RBX1 impairs its activity and promotes susceptibility to ER stress induction.     

Comparative study on the antibiotic susceptibility and plasmid profiles of Vibrio alginolyticus strains isolated from four Tunisian marine biotopes

The antibiotic resistance patterns and the plasmids profiles of the predominant etiological agent responsible for vibriosis in Tunisia, V. alginolyticus were studied to contribute to control their spread in some Mediterranean aquaculture farms and seawater. The sixty-nine V. alginolyticus strains isolated from different marine Tunisian biotopes (bathing waters, aquaculture and conchylicole farms and a river connected to the seawater during the cold seasons) were multi-drug resistant with high resistance rate to ampicillin, kanamycin, doxycyclin, erythromycin, imipinem, and nalidixic acid. The multiple resistance index ranged from 0.3 to 0.7 for the isolates of Khenis, from 0.5 to 0.8 for those of Menzel Jmil, from 0.5 to 0.75 (Hergla) and from 0.3 to 0.7 for the isolates of Oued Soltane. The high value of antibiotic resistance index was recorded for the V. alginolyticus population isolated from the fish farm in Hergla (ARI?=?0.672) followed by the population isolated from the conchylicole station of Menzel Jmil (ARI?=?0.645). The results obtained by the MIC tests confirmed the resistance of the V. alginolyticus to ampicillin, erythromycin, kanamycin, cefotaxime, streptomycin and trimethoprim. Plasmids were found in 79.48?% of the strains analyzed and 30 different plasmid profiles were observed. The strains had a high difference in the size of plasmids varying between 0.5 and 45?kb. Our study reveals that the antibiotic-resistant bacteria are widespread in the aquaculture and conchylicole farm relatively to others strains isolated from seawater.     

Single-surgeon experience of 87 buccal mucosal graft harvests

Although buccal mucosa has been the preferred graft material for use in the reconstruction of anterior urethral strictures for approximately 20 years, the plastic surgery literature is lacking in studies describing and evaluating this technique. The authors sought to report their experience with the technique of buccal mucosa graft harvest for use in urethral reconstruction. The authors identified 87 consecutive patients who underwent buccal mucosal graft harvesting during a 15-year period from 1995 to 2010. All donor sites were closed primarily. Preoperatively, a specialty-specific evaluation was performed by plastic surgeons and urologists. Postoperative donor-site morbidity was followed clinically. Eighty-seven patients underwent buccal harvesting. A single buccal graft was harvested in 75 patients (86.2 percent) and bilateral grafts were harvested in 12 patients (13.8 percent). The median patient age of the patients was 42 years (range, 16 to 78 years). There were no major intraoperative or postoperative complications. Minor complications included mild discomfort, numbness, cheek swelling, and restriction of oral movement, all of which resolved by the 3-month postoperative visit. The ability to eat and drink postoperatively was diminished during only the first 24 to 48 hours in all patients. Our series provides a 1-year follow-up in a substantial cohort looking at clinical outcomes after buccal harvesting. These results confirm the safety and efficacy of buccal mucosal harvesting to provide an effective and cosmetically superior option for urethral reconstruction. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, IV.     

The dynamics of sexual contact networks: effects on disease spread and control

Sexually transmitted pathogens persist in populations despite the availability of biomedical interventions and knowledge of behavioural changes that would reduce individual-level risk. While behavioural risk factors are shared between many sexually transmitted infections, the prevalence of these diseases across different risk groups varies. Understanding this heterogeneity and identifying better control strategies depends on an improved understanding of the complex social contact networks over which pathogens spread. To date, most efforts to study the impact of sexual network structure on disease dynamics have focused on static networks. However, the interaction between the dynamics of partnership formation and dissolution and the dynamics of transmission plays a role, both in restricting the effective network accessible to the pathogen, and in modulating the transmission dynamics. We present a simple method to simulate dynamical networks of sexual partnerships. We inform the model using survey data on sexual attitudes and lifestyles, and investigate how the duration of infectiousness changes the effective contact network over which disease may spread. We then simulate several control strategies: screening, vaccination and behavioural interventions. Previous theory and research has advanced the importance of core groups for spread and control of STD. Our work is consistent with the importance of core groups, but extends this idea to consider how the duration of infectiousness associated with a particular pathogen interacts with host behaviours to define these high risk subpopulations. Characteristics of the parts of the network accessible to the pathogen, which represent the network structure of sexual contacts from the “point of view” of the pathogen, are substantially different from those of the network as a whole. The pathogen itself plays an important role in determining this effective network structure; specifically, we find that if the pathogen’s duration of infectiousness is short, infection is more concentrated in high-activity, high-concurrency individuals even when all other factors are held constant. Widespread screening programmes would be enhanced by follow-up interventions targeting higher-risk individuals, because screening shortens the expected duration of infectiousness and causes a greater relative decrease in prevalence among lower-activity than in higher-activity individuals. Even for pathogens with longer durations of infectiousness, our findings suggest that targeting vaccination and behavioural interventions towards high-activity individuals provides comparable benefits to population-wide interventions.     

Overcoming regulatory and economic challenges facing pharmacogenomics

The number of personalized medicines and companion diagnostics in use in the United States has gradually increased over the past decade, from a handful of medicines and tests in 2001 to several dozen in 2011. However, the numbers have not reached the potential hoped for when the human genome project was completed in 2001. Significant clinical, regulatory, and economic barriers exist and persist. From a regulatory perspective, therapeutics and companion diagnostics are ideally developed simultaneously, with the clinical significance of the diagnostic established using data from the clinical development program of the corresponding therapeutic. Nevertheless, this is not (yet) happening. Most personalized medicines are personalized post hoc, that is, a companion diagnostic is developed separately and approved after the therapeutic. This is due in part to a separate and more complex regulatory process for diagnostics coupled with a lack of clear regulatory guidance. More importantly, payers have placed restrictions on reimbursement of personalized medicines and their companion diagnostics, given the lack of evidence on the clinical utility of many tests. To achieve increased clinical adoption of diagnostics and targeted therapies through more favorable reimbursement and incorporation in clinical practice guidelines, regulators will need to provide unambiguous guidance and manufacturers will need to bring more and better clinical evidence to the market place.